One of the most extreme stars in the universe has gotten evenwackier.

The most massive star discovered so far is called PSR J0952-0607, and it has a mass of 2.35 times that of the sun.

This is very close to the upper mass limit of 2.3 solar mass for neutron stars, which is an excellent laboratory for studying these ultra dense stars at what we think is the brink of collapse, in the hope of better understanding the weird quantum state of the matter.

Alex Filippenko is an astronomer at the University of California, Berkeley.

When you have one-and-a-half solar mass of this stuff, it's not at all clear how they will behave.

The collapsed cores of massive stars were between 8 and 30 times the mass of the Sun before they exploded.

The only denser object in the universe is a black hole.

Their mass is packed into a sphere just 20 kilometers or so across, and at that density, protons and electrons can combine into neutrons. The force it would take for the ball of neutrons to fall into a black hole is the only thing keeping it from happening.

This means that the stars are similar to atomic nuclei. It's difficult to say what will happen at this tipping point, where neutrons form exotic structures or blur into a soup of small particles.

One of the most interesting stars in the universe was PSR J0952-07. A pulsar is a star that spins fast and emits radiation from the poles. The poles sweep past the observer so that the star appears to pulse.

The rotation rate of these stars can be insane. The second-fastest pulsar in the Milky Way is called PSR J0952-07. A rotation rate of 716 times per second is the fastest.

It is also called a black widow. The star is so close to its companion that material is pulled from it. The material forms an accretion disk that whirls around and feeds into the star. The star's spin rate increases as the accretion disk's spin rate increases.

The team led by Roger Romani wanted to understand how PSR J0952-07 fit into the process. The star is less than 10 percent of the Sun's mass. A new, precise measurement for the pulsar was obtained from the research team's studies of the system and its elliptical path.

The result was 2.35 times the mass of the sun. If a standard star starting mass is around 1.4 times the mass of the Sun, then PSR J0952-0607 has slurped up an entire Sun's worth of matter. The team says it's important to have this information.

Some of the strongest constraints on the property of matter are provided by this. Many popular models of dense-matter physics are not included.

A high maximum mass for neutron stars suggests that it is a mixture of nucleus and dissolved up and down quarks all the way to the core." Many proposed states of matter are not included.

There is a mechanism that isolated pulsars can have millisecond rotation rates. J0952-0607's companion is almost gone; once it's completely devoured, the pulsar will retain its fast rotation speed for quite some time.

It will be the same as the other isolated millisecond pulsars.

Material spills over to the neutron star when the companion star becomes a red giant. A wind of particles comes out from the neutron star when it spins up. Filippenko said that if more time passes, the donor star's mass will decrease to that of a planet.

That is how lone millisecond pulsars could be created. They weren't all alone to begin with, they had to be in a pair, and now they're alone.

The research has appeared in a journal.